Method and apparatus for desuperheating steam



April 14, 1931. J. R. McDERMET 1,800,740

METHOD AND APPARATUS FOR DESUPERHEATING STEAM Filed April 29, 1926 2Sheets-Sheet 1 April 14, 1931- J. R. M DE RMET 1,300,749

METHOD AND APPARATUS FOR DESUPERHEATING STEAM Filed April 29, 1926 2Sheets-Sheet 2 m m H Patented Apr. 14, 1931 UNITED STATES PATENT OFFICEJOHN R. MCDERMET, JEANNETTE, PENNSYLVANIA, ASSIGNOR TO ELLIOTT COM-PANY, F JEANNETTE, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA METHODAND APPARATUS FORDESUPERHEATING STEAM Application filed April 29,

The present invention relates broadly to the art of heat exchanging andmore particularly to an improved method and apparatus for treatingsuperheated steam by means of which the superheat may be destroyed in aneffective and uniform manner.

At the present time, it is not uncommon practice to deliver superheatedsteam from the more modern boiler installations. Not

infrequently a portion, at least, of such steam is utilized withapparatus which has constituted part of a standard installation whichhas been in use for many years. Such apparatus is frequently not adaptedfor the use of high temperature superheated steam, partly perhaps,because the temperature of the superheated steam may injure some of theapparatus in processes where steam is utilized for heating and partlyalso because more or less obsolete equipment as referred to, is not ableto handle such superheated steam. In such cases the use of adesuperheater is imperative.

The present invention has for certain of its objects the provision of animproved method and apparatus" for effectively desuperheating steam, theinvention contemplating the mixing of water with steam. Under theseconditions, a portion of the water so mixed with the steam is evaporatedto an extent determined by the heat value of the superheat in the steam.The desuperheated steam then passes onward from the desuperheater at atemperature corresponding to its pressure, but in an increased amountdue to the destruction of the superheat and the evaporation of waterused in the process.

It is a further object of the present invention to provide a control anda method of 49 control which is adaptable for use with desuperheatersgenerall and which is not limited in its utility to t e construction andoperation of any particular type of desuperheater.

In the accompanying drawings there are shown, for purposes ofillustration only, two different embodiments of the present invention,it being understood that the drawings aremore or less diagrammatic forpurposes 50 of illustration only, and that they do not de- 1926. SerialNo. 105315.

illustrating one embodiment of the invention, 1-

and

Figure 2 is a view similar to Figure 1 illustrating another. embodimentof the invention. In approaching the problem of effectivelydesuperheating steam, it is necessary to bear in mind the fact that thetemperature of saturated steam is a function of its pressure, thetemperature and pressure being in exact agreement with standard steamtable values. In practical operation, however, there is no such thing asa constant steam pressure, and in all commercial existing boiler linesthe steam pressure is variable to at least some extent. It is obvious,therefore, that the temperaturefunction related directly to pressure,which in turn, is a more or less variable quantity, is not a functionwhich can be efi'ec tively and satisfactorily utilized for obtaining thedesired control of the desuperheating process.

In effecting a desuperheating operation it is necessary to admitsufficient Water to dostroy the superheat of the steam and reduce it toa saturated temperature, which temperature, as before pointed out, is afunction of a variable pressure. It becomes apparent, under theseconditions, that with any method of controlling a desuperheater, whilethe result to be obtained is the control of the temperature of the steamand make it correspond to the saturated value of the pressure, thistemperature function, the control of which is desired, cannot beutilized as an actuating medium.

The present invention involves, under these circumstances, the peculiarcondition that while the temperature is the thing which is to becontrolled, the control must be effected by means other than thetemperature, and the 7 present invention contemplates an operation basedupon such conditions. p e As previously pointed out, the inventioncontemplates the destruction of superheat by 'ineans of mixing waterwith the steam under such conditions that saturated steam s de-v liveredat a saturated temperature correspending to the pressure, the operationof de-v superheating involving the 1 quantity ofwaterin accordance withthe heat evaporation of a ,valu'e'of the superheat" destroyed Also, thedesuperheater under such conditions ofoperation does not deliver steamat a constant temperature, but at a temperature value variable inaccordance with the steam pressure.

In Figure 1 of the drawings there is illustrated more or lessdiagrammatically, eile'ctive means not only for bringing water intoContact with superheatedsteannbut alsofor controlling the supply ofwater. by means other than theltemperature, whereby satu-' rated steamis delivered by the desuperh'eate'r at a temperature corresponding tothe pressure of the steam. In the drawings there is illustrated adesuperhe'ater 2 conveniently comprising a casing having a more or lesscomplicatedbaflle arrangement '3 therein over .7 which water is adaptedto pass from an inlet 4' in contact withsuperheated steam supplied tothe casing through an inlet15. By reason of thecontact of the steam andwaterunder such conditions an eiiectfive heat interchange p e ismadepossible, thesuperheatof the steam is to V V 7 Connected tothereceiverT is a suitable float 110115111 10 'containin a lo-at o'l'stand destroyed, vand the steamleaves the desuperheater throughtheoutlet 6 as saturated steamm 1 i 1 Arranged below the desuperheater isa. re-: ceiver 7,which maybeof anydesired construc- V tion'adaptedtoreceive water from the de-a sup'erheater and,therefore,being,incommuni-- cation with the interior of the casingQL, The

Y receiver is.- provided with a discharge '8, the fiovvthrough which ispreferably controlled acalibrated orifice 9 ofsuch size as to dischargeonly, a comparatively small amount of water continuously from thereceiver space.-

Itwillbe, understood that with such an orifice the dischargeof waterwill be a natural function ofpressure differential between the receiverspace and the region into which the wateris discharged. This dischargedwater represents waste water which may be conveyed to any suitablepointor otherwise utilized in any manner that may be desired. Its

purpose is tosecure the desired sensitivity of operation oftheapparatusby the control of the supplied water, whereby saturated steamis delivered by 'the'desuperheater at a temperature corresponding to thepressure of the steam. I

ard' construction, not shown, suitably connecte'dbylinkage 11 to a floatoperated valve 12 in the inlet a, whereby the tloatwill'be effective foropening the valve 12 to admit lowers and to admit less water tothedesuperheater as thelevel in the float chamber rises. The float chambermay be connected in known manner to the interior of the, desuperheaterby means of a balancing connection 13', as well understood in the art,and may be provided with gauge glass 14 for visibly indicating waterlevel conditions therein,

WVith a constri'ictionfof the general nature referred to, operated inaccordance "withthe present invention, there 'is contemplated a supply01 desuperheating'water which, for purposes of convenience, descriptionand con- 'sideration-, may be divided into two quantities, A andB. Thequantity A represents" more water as thelevel in the float chamber thatwhich is evaporated in the desuper heating. process and passes from thecasing of the desuperheater as steam, whilethe quantity B represents anadditionaliamo'unt discharged fromthe desuperheater into the receiver"for-the purpose'of helping maintain the level in the receiver inopposition to the discharge through the orifice 9 The valve 12 willadmit water to the desuperheaterin accordance with the sum of thesetwo-quantities. V i, a V

By-reason of the orifice 9, a surplus of'wat'er may be delivered to thedesuperheater; and

thence to'the receiver and continuouslytdis charged therefrom: inaccordancewith the difi erentialpressure between the receiver space'andthe region into which the discharge takes place, the surplus representedby the quantity B'being, however, generally proportional tothe amountdelivered; The drain through the orifice therefore, insures afluctuation in the, water level within 4 the receiver, which fluctuationrepresents a possible means of control of the de'superheatingoperation.-

The quantityA supplied to the de's'uperheater anddefined as-beingevaporated, necessarily varies according to the amount of superheatwhicliit is necessary; to destroy, and consequently, upon thesaturatedtem- "perature of the steam delivered'by the nethis.quantitydrain-ed the quiet Water in the receiver would, in theory,establish alevel which would besubstantialiy unvariable, but whichinpractice would steadily increase until the entire device becameflooded. The quantity B, therefore, makes the water level in thereceiver variable and'controllable and enables this variation in levelto be utilized throu hthe float valve for varying the supply water tothe desuperheater.

Under. the foregoing conditions of opera tion, the quantityA varies overa Widelimit, the quantity A being arbitrarily selected by thedesuperheater in accordance with its demand and the quantity B beingrejected in the receiver to vary the water level and hence the load.Since the quantity B delivered to the receiver is interlinked with thequantity A evaporated in the desuperheating process, the level in thereceiver will rise or fall depending upon the ratio of B to the amountof water discharged by the orifice. The level control device will,therefore be actuated and will in turn control the delivery to thedesuperheater of a quantity of water A and B, the A component of whichis variable with outside conditions beyond any control of the leveldevice.

In Figure 2 there is indicated a generally similar form ofdesuperheating apparatus in which parts corresponding to the partsalready described are designated by the same reference charactershaving, however, a prime itlllXBCl thereto. In the form of Figure 2there is indicated a boiler level control device which in the drawingsis illustrated as comprising atube which may be partially filled withwater and partially filled with steam at the upper level, and operatingthrough the volatility of an enclosed gas, as will be understood in theart through the connection 11 for operating the control valve 12. Thisconstitutes a conventional type oi boiler regulation.

While the desuperheaters themselves as hereinbefore pointed out may beof any desired construction, they are herein illustrated as being of thegeneral construction disclosed and claimed in my copending application,Serial No. 651,301, filed July 13, 1923.

Certain advantages of the present invention arise from the provision ina desuperheating apparatus of means for controlling the temperature ofthe saturated steam delivered thereby by means other than thetemperature function.

Other advantages of the present invention arise from the provision of adesuperheating operation in which a total amount of water delivered tothe desuperheater is divided into quantities, one of which is determinedby the demand of the desuperheater and the other of which represents ameans of control for the supplied water. 1

Still other advantages of the invention arises from the provision of adesuperheating installation embodying a receiver receiving water from adesuperheater and operative to continuously discharge a predeterminedamount of water whereby a fluctuation in water level within the receiveris insured of such nature that it may be effectively utilized perheaterhavinga superheated steam inlet and a saturated steamoutlet, means forsupplying water to the desuperheater, a receiver.

communicating with the desuperheater and having a water inlet and afixed water discharge materially smaller than the inlet, and meansoperable in accordance with level variations in the receiver forcontrolling the supply 01 water to the desuperheater.

2. In a desuperheating apparatus, a desuperheater having a superheatedsteam inlet, a saturated steam outlet, float operated means formaintaining a substantially constant temperature of the saturated steamdeliveredthrough said outlet and connections for continuouslywithdrawing an arbitrary water quantity from the desuperheater.

3. In the method of desuperheating steam, the steps comprising supplyingsuperheated steam, supplying water to the superheated steam fordesuperheating purposes, collecting a portion of the water so supplied,controlling the supply of water by the quantity collected formaintaining a substantially constant saturated steam temperature, andcontinuously withdrawing an arbitrary water quantity from thedesuperheater. i

.In the method of desuperheating steam, the steps comprising bringingsuperheated steam and water into contact, collecting a portion of thewater, controlling the amountof water by the amount collected forcontrolling the temperature of the steam and make it correspond to thesaturated value of the pressure, and continuously withdrawing anarbitrary water quantity from the desuperheater.

5. In the method of desuperheating steam, the steps comprising bringingthe superheated steam into contact with water divisible into a quantityrepresenting that to be evaporated, and a second quantity arbitrarilydetermined, utilizing said second quantity for controlling the supply ofwater, and continuously withdrawing a quantity of Water arbitrarilydetermined. 1

6.. In the method of desuperheating steam, the steps comprising bringingthe superheated steam into intimate contact with a supply of water,controlling said supply to provide aquantity representing that to beevaporated in the desuperheating process and a second quantityarbitrarily determined, utilizing said second quantity for varying thesupply of water, and continuously withdrawing a quantity of waterarbitrarily determined.

7; In the method of .desuperheating, the steps comprising delivering toa desuperheater an amount of water to be evaporated in a desuperheatingprocess plus an additional amount, draining such additional amount tromthe desuperheater to provide a variable Water level in connectiontherewith, delivering the superheated steam to the desuperheater andutilizing said variable levelto control the supply of 'Water tothedesuperheaten h 8.7 In the method of;desuperheating steam,

the steps comprising supplying to 'aldesuperheater an amount ofWate'rin'excess of that re quired forthe desuperheating operation, constantlydraining a predetermined quantity of ater from the desuperheater, anduilizing variations-"in level caused by differences be tween the amountsdrained and the excess respond to the saturatedvalue ofthe pressure, andpassing the nections. a

In testimony whereof I have hereunto set my hand. i

supplied for controlling: the supply of ater 7 to the desuperheater.

'9. In the method of desuperheatingsteam, t V the steps comprisingsupplying superheated steam, supplyingwater to the superheated steam fordesuperheating purposes, control-' 1 ling the supply ofwaterformaintaining a substantially constant saturated steam temperature, continuously. Withdrawing a less amount of water than thatsupplied, and utilizingthe'water corresponding to the differ- ,encebetWen thatsuppliedand'the amount used and withdrawn for controlling theWater supplied,

' 10. In the methodof desuperheating steam, the steps comprisingbringing the superheated steam'into contact With Water divisible' intolaquantity representing that to be evaporated and a secondquantity'arbitrarily' determined, utilizing said second'quantity forcontrolling the supply of ater, and continuously withdrawin'g'fromContact with the steam an amount of Water substantially equal to sai'dsecond quantity.

11. 'In'the method of desuperheatin'g steam,

' the-steps comprising bringingthe super heated steam into contact withWater divisi- V J. R. llloDERME T. v V

saturated-steam to 'other'con- V 12. 1 themethod ofdes'uperheatingsteam, 7

the steps comprising bringing theflsuper heated steam into contact withWater divisible into a quantity representing that to be evaporated and asecondquantity arbitrarily determjine d,-utilizing' said second quantityfor controlling the supply of water, and continu-' I ously WithdrawingWater as such at a rate ma- 13; Inthe'method'of'desuperheating steam.

the steps comprising supplying superheated steam, supplying water tothesuperheated steam for desuperheating purposes,- continuously"withdrawing a portion of the supplied v Water, controlling the supplyofwater inaccordance with the excess between the supply and the amountrequired for controlling the temperature of the steam and'making it"cor-Y terially slower than the rate of'water sup- Pliedw I

